(1) Field of the Invention
The present invention relates generally to the control of an underwater vehicle trajectory from a moving platform, and more particularly to an adaptive trajectory selection apparatus and method that continually determines, in real-time, the trajectory of an underwater vehicle in order to effectively guide it to a desired area. Improved guidance is provided, in accordance with a given set of goals, through the innovative combination and extension of technologies and techniques from the fields of guidance and control, data management and expert systems.
(2) Description of the Prior Art
Present submarine combat control systems require an operator to select a single mode (trajectory) for post-launch guidance of an underwater vehicle, such as a torpedo. The post-launch guidance problem is that phase of vehicle/torpedo guidance whereby commands are sent over a communication system in order to guide the vehicle to the vicinity of a contact or target. In the case of a torpedo, effective guidance to the vicinity of the target will result in the torpedo's internal homing system detecting the contact (acquisition) and then beginning to autonomously seek it. Present systems cease any further vehicle control beyond acquisition.
Information on the contact is provided by sensors on the launching vessel. This data in conjunction with vessel navigational parameters, environmental and historical data is processed in order to provide estimates of contact state (position and velocity) along with indications of the quality of these estimates. The amount of either measured or estimated information available on a particular contact at any given time depends on many tactical and environmental factors. In present systems, a system operator monitors the system in order to determine what information is present and then selects a guidance mode when the torpedo is launched. At present, the modes from which the operator makes a choice for the post-launch guidance phase include: bearing rider, pursuit and intercept. A brief description of the characteristics of these trajectories follows.
Bearing rider is a mode whereby the vehicle or a point in front of the vehicle (associated with the acoustic homing system) is controlled so as to remain on the bearing between the firing platform and the contact. Pursuit is a trajectory in which the heading of the vehicle is controlled so as to always point at the contact. The intercept trajectory requires that the course of the vehicle be computed so that the vehicle will collide with the contact, which is assumed to be non-maneuvering, at some time in the future Upon selection of one of these modes, error indications are computed in the combat systems and the operator uses his judgement to determine when and what commands should be issued over the communication link to the torpedo to follow the selected trajectory. The ability to compute the required torpedo orders for any particular trajectory is dependent on the information content of the state vector for the contact-of-interest.
Traditionally, the guidance mode of choice during tactical encounters has been intercept. The drawback of intercept guidance is the requirement for a complete target state solution, i.e. Range, Course, Speed and Bearing. More recently this form of guidance is becoming less effective as a result of increased contact capabilities. Improved contact sensor capabilities allow for earlier alertment to an incoming vehicle/threat, thereby allowing for contact evasive action. This makes it impossible for the launching platform's combat system to maintain the complete contact motion solution set necessary to employ intercept throughout the launch to acquisition phase of a tactical encounter. The resulting reduced solution set thus requires an alternate strategy that is more in accordance with the available information.
Although the situation may warrant it, the guidance mode selected is rarely, if ever, changed during a given torpedo run. Further, if the present torpedo trajectory interferes with the contact data being measured by the launching vessel, modifications to the trajectory would be desirable in order to support the ongoing contact location estimation process. Such interference results in the launching vessel's sensor(s) obtaining heavily biased contact measurement information. This heavily biased information can seriously effect the ability to determine effective corrections necessary to sustain any form of vehicle trajectory control. It can also mask the presence of a contact maneuver which could obviously have serious impact on the efficacy of the guidance mode being employed.
Current post-launch guidance requires a great deal of operator involvement. A more automated system which reduces operator involvement is sorely needed in order to effectively react to the increasingly complex tactical missions/scenarios. Future anti-submarine warfare (ASW) scenarios will involve multiple sensors and concurrent guidance of multiple vehicles including torpedoes, mobile mines, autonomous underwater vehicles (AUV) and mobile countermeasures. Thus, current systems do not provide for continuous, real-time, adaptive selection of vehicle strategies and the associated automatic guidance desired to effectively employ single and multiple vehicles in a changing tactical scenario.